Magnetic sphere for use in a pipeline

ABSTRACT

A spherical pigging device for passage through a pipeline wherein magnetic sensors are located exterior to the pipeline. The device includes a non-ferrous spherical body. A plurality of magnets, each magnet having its poles radially aligned, are divided into two groups, a first group having its north poles facing the center of the spherical body and a second group having its north poles facing away from the center of the sphere.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spherical pigging device for passagethrough a pipeline which may be detected by magnetic sensors locatedexternal to the pipeline.

2. Prior Art

Pipeline "pigging" devices are used for cleaning, testing, gauging oroperating a pipeline and are adapted to fit in sealable engagement withthe interior of the pipeline. The pigging device may be moved throughthe pipeline in a number of ways. One way is to pressurize the pipelinewith fluid behind the device to move it through the pipeline.

The need to detect passage of solid objects such as pigging devicesmoving through pipelines has been served by a number of instruments. Adetection mechanism or signalling device senses movement of protrusionsthrough the pipeline. One type of sensing device is physically attachedto the pipeline through an opening and functions throughout the life ofthe pipeline. Usage may vary from every few hours to every few years.Periodic maintenance is required which requires special equipmentoperated by trained personnel that is performed on operating pipeline.If the signalling device is not maintained, it may leak the pipelinecontents into the environment and impair the operability of thesignalling device.

To alleviate the need for an opening to be cut into the pipeline andfrequent maintenance, several types of non-intrusive signalling deviceshave been developed. One type of non-intrusive signalling device sendsultrasonic signals through the pipeline wall to sense the location ofthe pig. The ultrasonic devices are relatively expensive, require tightphysical attachment to the pipe wall and have to be tuned with relationto the substance inside the pipeline.

Another type of non-intrusive signalling device senses the magneticfield change when a pig containing a magnet passes the signallinglocation. The pipeline wall is magnetically saturated with the magneticfield extending well outside the wall. A number of different devices ofmagnetic non-intrusive signalling devices have been produced. Themagnetic non-intrusive signalling device is typically inexpensive, iseasily mounted to the pipeline, is relatively small and is easilytransportable. Additionally, the magnetic type of non-intrusivesignalling device is relatively unaffected by the substance within thepipeline. The magnetic signalling device must, however, be used with apig that has magnets on the pig.

The majority of pipeline pigs are composed of a number of cups forming atubular body or a number of disks connected to a tubular body. A barmagnet is typically added to the tubular body with the poles of themagnet displaced axially along the axis of the pig body. The poleorientation of the magnet with respect to the axis of the pipeline is,therefore, maintained by the cups or the disks of the pig.

Another type of pipeline pig is a sphere which may be inflatable.Spherical pigs used in pipelines have a number of advantages. First,they are relatively easy to launch and receive. Second, the sphericalpigs will even travel well during bends in the pipeline. Third,spherical pigs can be inflated to compensate for wear which occurs overtime.

At the same time, however, a spherical pig is not restrained fromrolling or rotating and moving in the pipeline. Accordingly, themagnetic field of the simple bar magnet may not reach the signallingdevice. Additionally, the magnetic pole orientation, with respect to thepipeline of a bar magnet added to the sphere, would not be constant orcontrollable once moving in the pipeline.

In addition to the proposal for the use of a single magnet on a sphere,plural magnets on a sphere have also been proposed. An example is shownin U.S. Pat. No. 3,546,642 (Frederick et al.), wherein a plurality ofmagnets are disposed on a magnetic sphere. Each of the magnets is anindependent weak magnet having an independent magnetic field. Noprovision is made for coordinating the orientation of the magneticfields.

There is a need, therefore, for a spherical pigging device having aplurality of magnets wherein the magnetic fields of the magnets arecoordinated.

There is also a need to provide a process to produce a spherical piggingdevice wherein the magnets are embedded within the hollow body of thedevice and not subject to wear or breakage.

SUMMARY OF THE INVENTION

The present invention provides a spherical pigging device for passagethrough a pipeline.

The pigging device includes a non-ferrous spherical body wherein theexterior circumference of the body mates with and engages with theinside wall of the pipeline.

The spherical body is composed of an elastomeric material that isnon-ferrous. The spherical body is hollow having an interiorcircumference that may be inflated with a fluid during usage in thepipeline.

The pigging device includes a series of six permanent magnets. Eachmagnet is radially equidistant from the center of the spherical body.Each magnet is equidistant from each adjacent magnet. Each magnet isspaced from the exterior circumference of the spherical body so that itwill not engage with or be in contact with the pipeline. Each magnet isadditionally spaced from the interior circumference by a spacer.

Each of the six magnets is aligned with the radius of the sphericalpigging device. Pairs of magnets are aligned through the diameter of thedevice and have their poles aligned in the same orientation.

The magnets may be divided into two groups, a first group of threemagnets which have their north poles facing the center of the sphericalbody and a second group of magnets which have their north poles facingaway from the center of the spherical body. The first group of magnetsis in one hemisphere while the second group of magnets is in the otherhemisphere. While each magnet has its own magnetic field, the combinedeffect of the individual magnetic fields makes the spherical piggingdevice have a combined, total magnetic field similar to a bar magnetwith a north pole/south pole orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the spherical pigging device constructedin accordance with the present invention;

FIG. 2 is an enlarged view of a portion of the spherical body of thespherical pigging device shown in FIG. 1;

FIG. 3 is a diagrammatic representation of the arrangement of magnetsapart from the spherical pigging device itself; and

FIGS. 4, 5, and 6 illustrate the sequential steps to produce a sphericalpigging device in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in detail, FIG. 1 illustrates a sectional viewof a spherical pigging device 10 for passage through a pipeline (notshown). The pigging device 10 has been sectioned through a diameterthereof. The size of the pigging device will vary with the pipeline tobe used; it has been found that the present invention is applicable toall sizes of spheres.

The pigging device 10 includes a non-ferrous spherical body 12. Theexterior circumference 18 of the spherical body 12 will mate with andengage with the inside wall of the pipeline (not shown). Through usage,the exterior circumference 18 will wear under contact with the pipeline.The pigging device may be inflated to the appropriate size to compensatefor wear.

As will be described herein, the spherical body 12 will be composed ofan elastomeric material such as urethane which is somewhat pliable.Other material may be used, although it is preferable that the sphericalbody be non-ferrous, so that the body itself does not create orinterfere with a magnetic field.

It will be observed that the spherical body 12 is hollow having aninterior circumference 16. During use of the pigging device, thespherical body may be inflated with a fluid such as water (not shown).

The pigging device 10 includes a series of permanent magnets. In thepresent embodiment, six permanent magnets are employed. Four magnets arevisible in FIG. 1--magnets 20, 22, 24, and 26--which are each radiallyequidistant from the center of the spherical body 12. Each magnet isalso equidistant from each adjacent magnet. Each magnet is spaced fromthe exterior circumference of the spherical body 12 so that it will notengage with or be in contact with the interior of the pipeline.Accordingly, the magnets are protected from wear.

FIG. 2 shows an enlarged view of a portion of the spherical body 12 ofthe pigging device 10. One of the magnets 22 is visible within theinterior of the spherical body 12. The magnet 22 is spaced from theinterior circumference 16 by a spacer 32. Accordingly, the magnet is notsubject to wear or damage.

FIG. 3 is a diagrammatic representation of the arrangement of the sixmagnets apart from the spherical pigging device 10.

Each magnet 20, 22, 24, 26, 28, and 30 is aligned with the radius of thespherical pigging device. Magnets 20 and 26 are aligned through thediameter 60 of the device and have their poles aligned in the sameorientation. Magnets 22 and 24 are aligned through the diameter 62 ofthe device and have their poles aligned in the same orientation.Likewise, magnets 28 and 30 are aligned through the diameter 64 of thedevice and have their poles aligned in the same orientation.

It will be observed that the magnets may be divided into two groups, afirst group of magnets 20, 24, and 30 which have their north polesfacing the center of the spherical body and a second group of magnets22, 26, and 28 each have their north poles facing away from the center.The first group of magnets is in one hemisphere while the second groupof magnets is in the other hemisphere. While each magnet has its ownmagnetic field, the combined effect of the magnetic fields makes thespherical pigging device have a combined, total magnetic field similarto a bar magnet with a north pole/south pole orientation.

FIGS. 4, 5, and 6 illustrate the sequential steps required to produce aspherical pigging device 10 in accordance with the present invention. Inorder to produce the pigging device 10, initially a spherical core 40 isproduced. The core 40 is produced from a material that is liquid whenheated and solidifies or cures when cooled. One such material ismanufactured under the tradename PARAPLAST which is also capable ofdissolving in water.

The spherical core 40 may be cast with a hole or opening 42 through thediameter of the core. The six magnets (20, 22, 24 and 26 are visible inFIG. 4) are glued or otherwise affixed to the exterior of the core 40while it is still curing. Six spacers (32, 34, 36 and 38 are visible inFIG. 4) are glued or otherwise affixed under the magnets so that eachmagnet is spaced from the circumferential surface of the core 40. Aswill be seen herein, this assures that the magnet is ultimatelysurrounded or embedded within the spherical body 12 upon completion.

The next step is seen in FIG. 5. The core 40 is thereafter suspendedwithin a hollow spherical mold 50. The core 40 is concentrically alignedwith the spherical mold 50. This may be accomplished through use of arod 52 which extends through the opening 42 in the core and engages themold. At each end of the rod 52, between the spherical mold and thecore, valves 54 and 56 are installed.

A spherical space is thus produced between the core and the sphericalmold. Thereafter, urethane is poured into the mold in a liquid state.The mold with core may be rotated which tends to force any air bubblesoutward. In a preferred process, the urethane is cured in an oven for aperiod of time at approximately 200° F.

FIG. 6 illustrates the next step in the process to produce the sphericalpigging device 10. The spherical mold 50 is removed so that thesolidified spherical body 12 is revealed. The magnets (20, 22, 24, and26 are visible) are embedded within the spherical body.

As seen in FIG. 6, the core 40 is still within the spherical body. Thecore is cracked in a number of places by dropping the spherical body 12onto the ground. The resulting cracks will allow water to dissolve thecore 40 faster. The rod is removed and a water hose (not shown) isconnected to one of the valves while the other valve is forced open.Water entering the core will cause the core 40 to dissolve. Theresulting mixture will be flushed out of the opposite valve so that thebody is hollow.

Thereafter, the completed valve is illustrated in FIG. 1. The sphericalbody 12 may be inflated as a test to make sure that it adequately holdspressure. The pigging device may be shipped deflated with the corehollow. When the pigging device is used in the field in a pipeline, itwill be filled with water and pumped up to the correct size for theinterior diameter of the pipeline.

Whereas, the present invention has been described in relation to thedrawings attached hereto, it should be understood that other and furthermodifications, apart from those shown or suggested herein, may be madewithin the spirit and scope of this invention.

What is claimed is:
 1. A pig for passage through a pipeline where atleast one magnetic sensor is located, comprising:an elastomericspherical body having an exterior spherical surface and having a firstand a second hemispherical portion; and a plurality of permanent magnetspositioned within said spherical body in spaced apart locations andspaced from said spherical surface, each magnet having a north and asouth pole, the magnets being divided into a first group located withinsaid body first hemispherical portion and a second group located withinsaid body second hemispherical portion, said magnets in said first groupeach having said north pole facing towards said body spherical surfaceand said magnets in said second group each having said south pole facingtowards said body spherical surface.
 2. A pig for passage through apipeline according to claim 1 wherein said elastomeric spherical body ishollow.
 3. A pig for passage through a pipeline according to claim 2including at least one valve by which fluid may be injected into orremoved from said hollow spherical body.
 4. A pig for passage through apipeline according to claim 2 wherein said hollow spherical bodyprovides an interior spherical surface and wherein said magnets areadjacent to said interior spherical surface.